Nut plate

ABSTRACT

The invention provides a rivetless nut plate including a nut, a holding bracket having tubular and bracket portions, and a stem having an enlarged head. The stem is positioned within an aperture of the tubular portion such that the head is resting on a shoulder within the bracket aperture. The tubular portion is positioned within an aperture of a workpiece, such that the bracket portion rests on top of the workpiece. The nut is retained within the bracket portion. Force is applied to a bottom of the workpiece and another opposite force is applied to the stem such that the head expands the tubular portion radially outwardly such that lobes on the tubular portion become embedded into the wall of the workpiece, thereby securing the nut plate to the workpiece. The holding bracket could also be formed of two separate elements, a sleeve having a tubular portion and a bracket.

CROSS-REFERENCE

[0001] This patent application claims the benefit of domestic priorityof U.S. Provisional Application Serial No. 60/345,105, filed Nov. 9,2001, and entitled “Nutplate”.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a rivetless nut plate typicallyused in the aerospace industry.

[0003] Nut plates are used for attaching structural and non-structuralcomponents together in both aerospace and commercial applications. Thereare many different design configurations of nut plates being used today.Two major classes are riveted nut plates and flared rivetless nutplates.

[0004] In riveted nut plates, two or more rivets are employed forattaching the body of the nut plates to the workpiece.

[0005] Rivetless nut plates are composed fundamentally of threecomponents: a nut element, a holding bracket, and an attachment sleeve.The method of attachment and fixing of these nut plates to workpieces isbased on two major features:

[0006] (1) The insertion of the sleeve into an aperture of a workpieceby pressing in or pulling down the bracket sleeve assembly into theaperture of the workpiece. Serration/lobe features on the sleeveinterfere with walls of the workpiece to provide resistance against therotation of the nut plate.

[0007] (2) After insertion of the sleeve into the aperture of theworkpiece, an end of the sleeve is flared against the opposite side ofthe workpiece providing resistance against push-out forces that areencountered during usage of the nut plate.

[0008] One example of this type of rivetless nut plate is embodied inU.S. Pat. No. 4,732,518 which illustrates the insertion of a sleeveinside a workpiece against heavy interference forces and thendeformation of the sleeve to produce flaring of the end of the sleeve.The sleeve has a serration/lobe configuration thereon with theserration/lobe configuration being long and tapered such that theserrations/lobes extend into the walls of the workpiece. The taperedfeature, length and specific geometry are necessary to make installationpossible with the method of installation which was chosen for itsapplication. The main object of the '518 patent with its tapered andextended serration/lobe configuration was to enhance the fatigue life ofthe workpiece by distributing the load throughout the workpiece andproviding expansion due to the insertion of the sleeve into theworkpiece, and to cold work the material adjacent the perimeter of theworkpiece aperture.

[0009] The installation of rivetless nut plates with tooling of presentdesigns, however, such as those discussed in U.S. Pat. No. 4,732,518, iscumbersome, slow, complicated, costly and often non-functional. Also,the hole preparation needs to be precise and requires countersinking orcounterboring for flush installation. These shortcomings have limitedthe usage of rivetless nut plates.

[0010] The flaring of rivetless nut plates is also disadvantageous formany reasons, such as complicated tooling, special aperture preparation(such as counter-bore and counter-sink) to achieve flush installation,grip length limitations, the creation of gaps between the sleeve and thewalls of the workpiece, and longer length, thus making the rivetless nutplate a relatively heavy component.

[0011] Four other rivetless nut plate designs are illustrated in U.S.Pat. Nos. 5,096,349, 5,245,743, 5,405,228 and 5,704,747, which weredesigned to avoid flaring, but each has disadvantages associatedtherewith. The design of U.S. Pat. No. 5,704,747, relies on adhesive forattaching the nut plate to the structure. The designs of U.S. Pat. Nos.5,096,349, 5,245,743 and 5,405,228 do not have adhesives or lobes whichare used to fix the nut plate within the structure. These designs relyon heavily cold-worked holes and high interference engagement utilizinga hardened pin as the installation tool to expand the sleeve portioninto the structure. The sleeve is smooth and because of high levelexpansion, the friction of forces created is supposed to retain the nutplate and provide expected mechanical properties. The fundamentalpurpose for design of this fastener is to enhance mechanical fatigueproperties of the joint. The parts for this design are very expensive,installation is costly and cumbersome, and hole preparation needs to bevery precise. Thus, the overall cost of this design is very high andapplication is thereby limited. There are also reports in the field thatbecause of the required heavy expansion the receiving structure candeform beyond acceptable limits, thereby causing damage and rejection ofthe hole structure.

[0012] Thus, there is a need for a rivetless nut plate design whichovercomes the disadvantages of the prior art rivetless nut platedesigns. The present invention provides for such a rivetless nut platedesign.

OBJECTS AND SUMMARY OF THE INVENTION

[0013] A primary object of the invention is to provide a rivetless nutplate which will simplify the installation of rivetless nut plates toworkpieces.

[0014] An object of the invention is to provide a rivetless nut platewhich utilizes a novel tooling concept to speed up the installation ofthe nut plate to the workpiece and which ensures proper engagement ofthe sleeve of the nut plate to the workpiece.

[0015] Another object of the invention is to provide a rivetless nutplate which will greatly expand the usage of rivetless nut plate inaerospace applications as well as in commercial industry.

[0016] Yet another object of the invention is to provide a rivetless nutplate which satisfies the specified requirements of torque-out, which isthe ability to resist the specified twisting torque acted upon the nutplate around the axis of the hole.

[0017] Still another object of the invention is to provide a rivetlessnut plate which satisfies the specified requirements of push-out, whichis the ability to resist a specified applied force along the axis of thehole.

[0018] Another object of the invention is to provide a rivetless nutplate which satisfies the specified requirements of fatigue, which isthe installation characteristic which renders the receiving structureresistance to dynamic loading.

[0019] Still another object of the invention is to provide a rivetlessnut plate which combines the bracket and sleeve component into a singlecomponent, thereby reducing one part, in order to greatly simplifycomponent assembly, reduce overall cost, and improve functional andmechanical properties.

[0020] Yet another object of the invention is to provide a rivetless nutplate which does not allow for gaps to be formed between the sleeveportion of the nut plate and the walls of the workpiece uponinstallation of the rivetless nut plate.

[0021] Another object of the invention is to provide a rivetless nutplate which expands the sleeve within the aperture of a workpiece toensure intimate contact with the workpiece throughout the aperture andwhich induces residual compressive stresses which would enhance thefatigue life of the workpiece.

[0022] Yet another object of the invention is to provide a rivetless nutplate in which the nut may be easily replaced by another nut if thefirst nut is worn.

[0023] Still another object of the invention is to provide lobes or ribson the outer wall of a tubular portion inserted into an aperture of theworkpiece which will help provide improved push-out, torque-out andfatigue characteristics.

[0024] Briefly, and in accordance with the foregoing, the inventionprovides three embodiments of a novel nut plate.

[0025] The first embodiment of the invention provides a nut plate whichincludes a nut, a holding bracket and a stem. The holding bracket has atubular portion and a bracket portion. The tubular portion has anaperture therethrough which defines an inner wall which is tapered andwhich defines a shoulder. The tubular portion has an outer wall withlobes extending therefrom. The bracket portion extends from the tubularportion and has a pair of opposing sidewalls with flanges extendingtherefrom and slots provided therethrough. The nut has a base portionwith tabs extending from opposing sides thereof and a cylindricalportion with a threaded aperture therethrough extending upwardlytherefrom. The stem has an enlarged deformable head portion and anelongated cylindrical portion extending therefrom. In operation, thestem is inserted into the aperture of the tubular portion such that theenlarged head portion rests on the shoulder. The nut is then insertedinto the bracket portion of the holding bracket such that the tabs ofthe nut are positioned within the slots of the bracket portion to securethe nut and to allow float movement of the nut both laterally andlongitudinally relative to the bracket portion. The tubular portion isthen inserted into an aperture of a workpiece such that the bracketportion rests on top of the workpiece. The stem is then pulled throughthe aperture of the tubular portion to expand the tubular portion intothe wall defined by the aperture of the workpiece. The lobes on theouter wall of the tubular portion are embedded into the wall of theworkpiece to improve push-out and torque-out. As the head portion of thestem is pulled through the aperture of the tubular portion, the headwill deform to assume the geometry relevant to the expanded size of theexpanded inner wall of the tubular portion. Once pulled entirely throughthe aperture, the tubular portion is fixedly connected to the workpieceand the stem can be discarded.

[0026] The second embodiment of the invention provides a nut plate whichincludes a nut, a bracket, a sleeve, and a stem. The nut plate of thesecond embodiment is basically identical to the nut plate of the firstembodiment except that the holding bracket of the first embodiment isprovided in two separate pieces, namely, the bracket and the sleeve withthe sleeve being similar to the tubular portion of the holding bracketand the bracket being similar to the bracket portion of the holdingbracket. Operation of attachment of the nut plate of the secondembodiment is performed in virtually the same manner as attachment ofthe nut plate of the first embodiment.

[0027] The third embodiment of the invention provides a nut plate whichincludes a nut, a holding bracket, a stem and a retainer. The holdingbracket has a tubular portion and a bracket portion. The tubular portionhas an aperture therethrough which defines an inner wall which istapered and which defines a shoulder. The inner wall may also have a lipextending therefrom. The tubular portion has an outer wall with lobesextending therefrom. The lobes are a series of high and low lobes withthe high lobes having an angled portion proximate to the bracketportion. The bracket portion extends from the tubular portion and has abase with protrusions extending therefrom and a pair of opposingsidewalls extending therefrom having slots provided therethrough. Thenut has a base portion with recesses at opposing ends thereof and acylindrical portion with a threaded aperture therethrough extendingupwardly therefrom. The stem has an enlarged deformable head portion andan elongated cylindrical portion extending therefrom. The retainer ispreferably a spring member which can be fitted into the slots of thebracket portion. In operation, the stem is inserted into the aperture ofthe tubular portion such that the enlarged head portion rests on theshoulder. The nut is then inserted into the bracket portion of theholding bracket such that the recesses of the nut receive theprotrusions on the base of the bracket portion. The retainer is thenpositioned within the slots of the opposing sidewalls of the bracketportion such that the nut is retained between the retainer and thebracket portion, but is allowed to float both laterally andlongitudinally. The tubular portion is then inserted into an aperture ofa workpiece such that the bracket portion rests on top of the workpiece.The stem is then pulled through the aperture of the tubular portion toexpand the tubular portion into the wall defined by the aperture of theworkpiece. The high and low lobes on the outer wall of the tubularportion are embedded into the wall of the workpiece to improve push-outand torque-out, the high lobes moving material to the low lobes suchthat the low lobes create a seal with the wall of the workpiece. As thehead portion of the stem is pulled through the aperture of the tubularportion, the head will deform to assume the geometry relevant to theexpanded size of the expanded inner wall of the tubular portion. Oncepulled entirely through the aperture, the tubular portion is fixedlyconnected to the workpiece and the stem can be discarded.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The features of the invention which are believed to be novel aredescribed in detail hereinbelow. The organization and manner of thestructure and operation of the invention, together with further objectsand advantages thereof, may best be understood by reference to thefollowing description taken in connection with the accompanying drawingswherein like reference numerals identify like elements in which:

[0029]FIGS. 1a-1 c are side elevational cross-sectional views of the nutplate of a first embodiment of the invention being attached to theworkpiece;

[0030]FIG. 2 is a side elevational view of a holding bracket of the nutplate of the first embodiment of the invention;

[0031]FIG. 3 is a side elevational cross-sectional view of the holdingbracket of the nut plate of the first embodiment of the invention;

[0032]FIGS. 4a-4 g are perspective views of the holding bracket of thenut plate of the first embodiment of the invention each having adifferent configuration for the lobes or ribs on an outside wall of atubular portion;

[0033]FIG. 5 is a perspective view of an alternative design of the nutplate of the first embodiment of the invention;

[0034]FIG. 6 is a side elevational cross-sectional view of thealternative design of the nut plate as illustrated in FIG. 5;

[0035]FIG. 7 is an exploded perspective view of the nut plate of asecond embodiment of the invention;

[0036]FIG. 8 is a side elevational cross-sectional view of the nut plateof the second embodiment of the invention positioned within a workpieceprior to attachment of the nut plate to the workpiece;

[0037]FIG. 9 is a side elevational cross-sectional view of the nut plateof the second embodiment of the invention positioned within a workpieceafter attachment of the nut plate to the workpiece;

[0038]FIG. 10 is an exploded perspective view of the nut plate of athird embodiment of the invention;

[0039]FIG. 11 is a side elevational view of the nut plate of the thirdembodiment of the invention;

[0040]FIGS. 12a-12 c are side elevational cross-sectional views of thenut plate of the third embodiment of the invention being attached to theworkpiece;

[0041]FIG. 13 is a bottom perspective view of the holding bracket of thenut plate of the third embodiment of the invention;

[0042]FIG. 14 is a top perspective view of the holding bracket of thenut plate of the third embodiment of the invention;

[0043]FIG. 15 is a side-elevational cross-sectional view of the holdingbracket of the nut plate of the third embodiment of the invention; and

[0044]FIG. 16 is a side-elevational cross-sectional view of analternative holding bracket of the nut plate of the third embodiment ofthe invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

[0045] While this invention may be susceptible to embodiment indifferent forms, there is shown in the drawings and will be describedherein in detail, specific embodiments with the understanding that thepresent disclosure is to be considered an exemplification of theprinciples of the invention, and is not intended to limit the inventionto that as illustrated.

[0046] A first embodiment of a nut plate 100 is shown in FIGS. 1-6, asecond embodiment of the nut plate 200 is shown in FIGS. 7-9, and athird embodiment of the nut plate 300 is shown in FIGS. 10-16. Likeelements are denoted with like reference numerals with the firstembodiment being in the one hundreds, the second embodiment being in thetwo hundreds, and the third embodiment being in the three hundreds.

[0047] Attention is now directed to the nut plate 100 of the firstembodiment of the invention as illustrated in FIGS. 1-6. The nut plate100 of the first embodiment includes a nut 102, a holding bracket 104and a stem 106.

[0048] As best illustrated in FIGS. 2-3, the holding bracket 104 isgenerally Y-shaped in side elevation and includes a tubular portion 108and a bracket portion 110 which extends outwardly from the tubularportion 108 at a first end 112 thereof. The bracket portion 110 includesa base portion 114 and opposed upstanding side walls 116, 118. Flanges120, 122 extend from upper ends of the side walls 116, 118 and projectoutwardly therefrom. Slots 124, 126 extend through the side walls 116,118 of the bracket portion 110. The side walls 116, 118 and flanges 120,122 are preferably formed of a resilient material.

[0049] The tubular portion 108 extends in the opposite direction fromthe base portion 114 of the bracket portion 110 than do the side walls116, 118 of the bracket portion 110. The tubular portion 108 has anaperture 128 therethrough which defines an inner wall 130 of the tubularportion 108. The tubular portion 108 also has an outer wall 136. At thefirst end 112 of the tubular portion 108, the inner wall 130 defines afirst inner diameter of the aperture 128. At a minimal distance from thefirst end 112 of the tubular portion 108, the inner wall 130 tapersinwardly to provide a shoulder 132 and to define a second inner diameterof the aperture 128 and thus a wall thickness of the tubular portion 108between the outer wall 136 and the shoulder 132. The wall thickness ofthe tubular portion 108 between the outer wall 136 and the shoulder 132is preferably 0.010 inches. The second inner diameter of the aperture128 at the shoulder 132 of the tubular portion 108 is smaller than thefirst inner diameter of the aperture 128 at the first end 112 of thetubular portion 108. From the shoulder 132 to a second end 134 of thetubular portion 108, the inner wall 130 is tapered or stepped such thatthe inner wall 130 at the second end 134 of the tubular portion 108defines a third inner diameter and thus a wall thickness of the tubularportion 108 at the second end 134 of the tubular portion 108. The wallthickness of the tubular portion 108 at the second end 134 of thetubular portion 108 is preferably 0.014 inches and, thus, is larger thanthe wall thickness of the tubular portion 108 between the outer wall 136and the shoulder 132 of the tubular portion 108. The third innerdiameter of the aperture 128 at the second end 134 of the tubularportion 108 is smaller than the second inner diameter of the aperture128 at the shoulder 132 of the tubular portion 108.

[0050] The outer wall 136 of the tubular portion 108 extends from anundersurface 138 of the bracket portion 110 to the second end 134 of thetubular portion 108. Lobes or ribs 140 extend outwardly from the outerwall 136 of the tubular portion 108. The lobes 140 can be formed in manydifferent configurations on the outer wall 136, such as axiallystraight, tilted or helical, as illustrated in FIGS. 4a-4 g. Preferably,the lobes 140 are formed as illustrated in FIGS. 2 and 4b, with thelobes 140 being axially straight along the outer wall 136. Adjacentlobes 140 are positioned apart from one another such that gaps 141 areprovided between adjacent lobes 140. The lobes 140 also have an angledportion 143 proximate to the undersurface 138 of the bracket portion 110such that the lobes 140 are thicker proximate to the undersurface 138 ofthe bracket portion 110. The angled portions 143 of the lobes 140provide for improved torque of the bracket portion 110.

[0051] As illustrated in FIGS. 1a-1 c, the nut 102 includes acylindrical portion 142 and a flat base portion 144 which extendsoutwardly from the cylindrical portion 142 at one end thereof. Thecylindrical portion 142 has an aperture 146 therethrough which definesan inner diameter of the cylindrical portion 142. The cylindricalportion 142 at the inner diameter is generally threaded such that aworkpiece, such as a bolt, can be attached thereto. The flat baseportion 144 further defines tabs or wings 148, 150 that extend radiallyoutwardly in opposite directions. The tabs 148, 150 fit within the slots124, 126 of the bracket portion 110 of the holding bracket 104, suchthat the nut 102 is retained against the holding bracket 104 to preventsubstantial movement between the nut 102 and the holding bracket 104.The tabs 148, 150 are smaller in size than the slots 124, 126 in orderto allow the nut 102 limited floating movement relative to the holdingbracket 104.

[0052] As illustrated in FIGS. 1a-1 c, the stem 106 includes an enlargedhead portion 152 at a first end 154 thereof and an elongate cylindricalportion 156 which extends from the enlarged head portion 152. Theenlarged head portion 152 has a diameter which is smaller than the firstinner diameter of the tubular portion 108 but larger than the secondinner diameter of the tubular portion 108. The enlarged head portion 152tapers to the cylindrical portion 156, which has a diameter that issmaller than the third inner diameter of the tubular portion 108. Thecylindrical portion 156 has a tool engaging section 158 proximate to asecond end 160 of the stem 106. The enlarged head portion 152 may have acavity 162 provided therein to help in the deformation of the enlargedhead portion 152, as will be discussed further herein, although thecavity 162 need not be provided to deform the enlarged head portion 152.

[0053] In operation, the second end 160 of the stem 106 is inserted intothe aperture 128 of the tubular portion 108 of the holding bracket 104at the first end 112 thereof until the enlarged head portion 152 of thestem 106 meets resistance from the shoulder 132 of the inner wall 130 ofthe tubular portion 108, as illustrated in FIG. 1a.

[0054] The nut 102 is then connected to the holding bracket 104 bydeflecting outwardly the flanges 120, 122 and the side walls 116, 118 ofthe holding bracket 104 and inserting the tabs 148, 150 of the nut 102into the slots 124, 126 of the side walls 116, 118. The flanges 120, 122and the side walls 116, 118 are then allowed to return to their normalposition, thus connecting the nut 102 to the holding bracket 104,allowing for floating movement of the nut 102 relative to the holdingbracket 104, as illustrated in FIG. 1a.

[0055] The tubular portion 108 of the holding bracket 104 is theninserted into an aperture 164 of a workpiece 166, such that theundersurface 138 of the bracket portion 110 of the holding bracket 104sits on a top surface 168 of the workpiece 166, as illustrated in FIG.1b. The aperture 164 has a diameter which is slightly larger than adiameter of the tubular portion 108 of the holding bracket 104. Theaperture 164 has a length which is larger than or equal to a length ofthe tubular portion 108 of the holding bracket 104 such that the tubularportion 108 does not extend beyond the aperture 164 of the workpiece166.

[0056] A holding or abutment force F1 is applied to a bottom surface 170of the workpiece 166 and a tool (not shown) engages the tool engagingsection 158 of the stem 106 and applies a force F2 to the stem 106 whichis directed axially and in the opposite direction than the force F1 isapplied to the workpiece 166, as illustrated in FIG. 1b. The force F2 onthe stem 106 seats the tubular portion 108 and the bracket portion 110of the holding bracket 104 firmly against and within the workpiece 166.

[0057] Upon application of force F2 to the stem 106, the enlarged headportion 152 meets resistance from the shoulder 132 of the inner wall 130such that the inner wall 130 is forced to expand radially outwardly asthe enlarged head portion 152 deforms to the size of the expanded innerwall 130, with assistance from the cavity 162 in the enlarged headportion 152, if provided. As the inner wall 130 of the tubular portion108 is inwardly tapered or stepped from the shoulder 132 to the secondend 134 of the tubular portion 108, the enlarged head stem 152 willconsistently have an outer diameter which is larger than the diameter ofthe inner wall 130 of the tubular portion 108, even though the enlargedstem head 152 deforms to assume the geometry relevant to the size of theexpanded inner wall 130 of the tubular portion 108. Thus, the axialforce F2 applied to the enlarged stem head 152 will place a continuousexertion of radial expansion on the inner wall 130 of the tubularportion 108. As the inner wall 130 is continuously expanded by theenlarged head portion 152, the outer wall 136 of the tubular portion 108continuously expands radially outwardly within the aperture 164 againstthe wall of the workpiece 166, thus embedding the lobes 140 in the wallof the workpiece in a fixed and intimate engagement with the wall of theaperture 164. The angled portions 143 of the lobes 140 embed furtherinto the wall of the workpiece 166 to provide improved torque-out of theholding bracket 104. When the enlarged head portion 152 is pulledcompletely through the aperture 128 of the tubular portion 108, theholding bracket 104 is attached to the workpiece 166, as illustrated inFIG. 1c, and the stem 106 can be discarded. A workpiece, such as a bolt,can then be attached to the nut plate 100.

[0058] The enlarged head portion 152 of stem 106 will initially expandthe tubular portion 108 as well as place a compressive load on thecomponents to seat them against the upper surface 168 of the workpiece166. The tubular portion 108 will expand to engage the wall of theaperture 164 in the workpiece 166. As this occurs, radial forces areestablished which are sufficient to deform the head portion 152radially. Thus, the head portion 152 can handle tolerance variations inthe workpiece aperture 164, and will continuously deform the tubularportion 108 radially outward to engage the aperture wall with sufficientforce to cause the lobes 140, or alternate structure, on the outer wall136 of tubular portion 108 to embed in the wall of the aperture 164. Ascan be appreciated, the increasing wall thickness of the tubular portion108 insures that radial deformation continues along the entire length oftubular portion 108 to attain the desired degree of engagement of thelobes 140 in the wall of the aperture 164 such that improved torque-out,push-out and fatigue characteristics are achieved.

[0059] An alternative design of the nut plate 100 of FIGS. 1-4 isillustrated in FIGS. 5-6 and is referenced as nut plate 100 a. The nutplate 100 a includes a nut 102 a, a holding bracket 104 a, and a stem(not shown).

[0060] Attention is now directed to the second embodiment of the nutplate 200 as illustrated in FIGS. 7-9. The nut plate 200 of the secondembodiment includes a nut 202, a bracket 203, a sleeve 205, and a stem206. As the nut 202 and the stem 206 of the nut plate 200 are identicalin structure to the nut 102 and stem 106 of the nut plate 100 of thefirst embodiment, these components will not be described again hereinwith the understanding that the description of the nut 202 is identicalto the nut 102 and the description of the stem 206 is identical to thestem 106. Like reference numerals will denote like elements. In effect,the bracket 203 and the sleeve 205 are separate components in thisembodiment, whereas they are unitary in the previous embodiment as theholding bracket 104. Thus, the bracket 203 and the sleeve 205 combine toform a holding bracket 204.

[0061] The bracket 203 of the nut plate 200 is generally U-shaped inside elevation and includes a base portion 214 and opposed upstandingside walls 216, 218. Flanges 220, 222 extend from upper ends of the sidewalls 216, 218 and project outwardly therefrom. Slots 224, 226 extendthrough the side walls 216, 218 of the bracket 203. The side walls 216,218 and the flanges 220, 222 are preferably formed of a resilientmaterial. A relatively large circular opening 227 is formed at a centerof the base portion 214.

[0062] The sleeve 205 includes a tubular portion 208 and a head 209 thatextends perpendicular to the tubular portion 208 at a first end 211 ofthe sleeve 205. The head 209 defines tabs or wings 272, 274 that extendradially outwardly in opposite directions. The tabs 272, 274 fit withinthe slots 216, 218 of the bracket 203. The tubular portion 208 has anaperture 228 therethrough which defines an inner wall 230 of the tubularportion 208. At the first end 211 of the sleeve 205, the inner wall 230defines a first inner diameter. At a minimal distance from the first end211 of the sleeve 205, the inner wall 230 tapers inwardly to provide ashoulder 232 and to define a second inner diameter, with the secondinner diameter being smaller than the first inner diameter. From theshoulder 232 to a second end 213 of the sleeve 205, the inner wall 230is slightly tapered or stepped such that the inner wall 230 at thesecond end 213 of the sleeve 205 defines a third inner diameter, withthe third inner diameter being smaller than the second inner diameter,and such that the wall thickness of the tubular portion 208 is greaterat the second end 213 of the sleeve 205 than proximate to where theshoulder 232 is provided.

[0063] An outer wall 236 of the tubular portion 208 extends from anundersurface 276 of the head 209 to the second end 213 of the sleeve205. Lobes 240 extend outwardly from the outer wall 236 of the sleeve205. The lobes 240 can be formed in many different configurations on theouter wall 236.

[0064] In operation, the bracket 203 is placed on a top surface 268 of aworkpiece 266 having an aperture 264 such that the opening 227 of thebracket 203 is positioned in alignment with the aperture 264 of theworkpiece 266. The tubular portion 208 of the sleeve 205 is theninserted through the opening 227 of the bracket 203 and into theaperture 264 of the workpiece 266. The aperture 264 has a diameter whichis slightly larger than a diameter of the tubular portion 208 of thesleeve 205. The side walls 216, 218 of the bracket 203 are deflected toallow the tabs 272, 274 of the head 209 to be inserted into the slots224, 226 of the side walls 216, 218.

[0065] The second end 260 of the stem 206 is then inserted into theaperture 228 of the sleeve 205 at the first end 211 thereof until theenlarged head portion 252 of the stem 206 comes into contact with theshoulder 232 of the inner wall 230 of the sleeve 205.

[0066] The nut 202 is then connected to the bracket 203 by deflectingoutwardly the flanges 220, 222 and the side walls 216, 218 of thebracket 203 and inserting the tabs 248, 250 of the nut 202 into theslots 224, 226 of the side walls 216, 218 and on top of the tabs 272,274 of the head 209 of the sleeve 205. The flanges 220, 222 and the sidewalls 216, 218 are then allowed to return to their normal position, thusconnecting the nut 202 to the sleeve 205 and the bracket 203, allowingfor floating movement of the nut 200 relative to the bracket 203 and thesleeve 205.

[0067] A holding or abutment force F1 is applied to a bottom surface 270of the workpiece 266 and a tool (not shown) engages the tool engagingsection 258 of the stem 206 and applies a force F2 to the stem 206 whichis directed axially and in the opposite direction than the force F1 isapplied to the workpiece 266. The force F2 on the stem 206 seats thesleeve 205 and the bracket 203 firmly against and within the workpiece266.

[0068] Upon application of force F2 to the stem 206, the enlarged headportion 252 meets resistance from the shoulder 232 of the inner wall 230such that the inner wall 230 is forced to expand radially outwardly asthe enlarged head portion 252 deforms to the size of the expanded innerwall 230 with assistance from the cavity (not shown) in the enlargedhead portion 252, if provided. As the inner wall 230 of the tubularportion 208 is inwardly tapered or stepped from the shoulder 232 to thesecond end 213 of the sleeve 205, the enlarged head stem 252 willconsistently have an outer diameter which is larger than the diameter ofthe inner wall 230 of the tubular portion 208, even though the enlargedstem head 252 deforms to assume the geometry relevant to the size of theexpanded inner wall 230 of the tubular portion 208. Thus, the axialforce F2 applied to the enlarged stem head 252 will place a continuousexertion of radial expansion on the inner wall 230 of the tubularportion 208. As the inner wall 230 is continuously expanded by theenlarged head portion 252, the outer wall 236 of the tubular portion 208expands radially outwardly in the aperture 264 against the wall of theworkpiece 266, thus embedding the lobes 240 in the wall of the workpiece266 in a fixed and intimate engagement with the wall of the aperture264. When the enlarged head portion 252 is pulled completely through theaperture 228 of the tubular portion 208, the sleeve 205, and thus thebracket 203 and the nut 202 are attached to the workpiece 266 and thestem 206 can be discarded. A workpiece, such as a bolt, can then beattached to the nut plate 200.

[0069] The enlarged head portion 252 of stem 206 will initially expandthe tubular portion 208 as well as place a compressive load on thecomponents to seat them against the upper surface 268 of the workpiece266. The tubular portion 208 will expand to engage the wall of theaperture 264 in the workpiece 266. As this occurs, radial forces areestablished which are sufficient to deform the head portion 252radially. Thus, the head portion 252 can handle tolerance variations inthe workpiece aperture 264, and will continuously deform the tubularportion 208 radially outward to engage the aperture wall with sufficientforce to cause the lobes 240, or alternate structure, on the outer wall236 of tubular portion 208 to embed in the wall of the aperture 264. Ascan be appreciated, the increasing wall thickness of the tubular portion208 insures that radial deformation continues along the entire length oftubular portion 208 to attain the desired degree of engagement of thelobes 240 in the wall of the aperture 264.

[0070] Attention is now directed to the nut plate 300 of the thirdembodiment of the invention as illustrated in FIGS. 10-16. The nut plate300 of the first embodiment includes a nut 302, a holding bracket 304, astem 306 and a retainer 307. As the stem 306 is identical in structureto the stem 106 of the nut plate 100 of the first embodiment, thiscomponent will not be described again herein with the understanding thatthe description of the stem 306 is identical to the stem 106. Likereference numerals will denote like elements.

[0071] As best illustrated in FIGS. 13-15, the holding bracket 304 isgenerally Y-shaped in side elevation and includes a tubular portion 308and a bracket portion 310 which extends outwardly from the tubularportion 308 at a first end 312 thereof. The bracket portion 310 includesa base portion 314 and opposed upstanding side walls 316, 318. The baseportion 314 has a pair of protrusions 317, 319 which protrude upwardlyfrom the base portion 314. Protrusion 317 is provided proximate to edge321 of the base portion 314 and protrusion 319 is provided proximate toedge 323 of the base portion 314. Slots 324, 326 extend through the sidewalls 316, 318 of the bracket portion 310.

[0072] The tubular portion 308 extends in the opposite direction fromthe base portion 314 of the bracket portion 310 than do the side walls316, 318 and the protrusions 317, 319 of the bracket portion 310. Asbest illustrated in FIG. 15, the tubular portion 308 has an aperture 328therethrough which defines an inner wall 330 of the tubular portion 308.The tubular portion 308 also has an outer wall 336. At the first end 312of the tubular portion 308, the inner wall 330 defines a first innerdiameter of the aperture 328. From the first end 312 of the tubularportion 308, the inner wall 330 curves inwardly to provide a shoulder332 and to define a second inner diameter of the aperture 328 and thus awall thickness of the tubular portion 308 between the outer wall 336 andthe shoulder 332. The wall thickness of the tubular portion 308 betweenthe outer wall 336 and the shoulder 332 is preferably 0.010 inches. Thesecond inner diameter of the aperture 328 at the shoulder 332 of thetubular portion 308 is smaller than the first inner diameter of theaperture 328 at the first end 312 of the tubular portion 308. From theshoulder 332 to a second end 334 of the tubular portion 308, the innerwall 330 is tapered or stepped such that the inner wall 330 at thesecond end 334 of the tubular portion 308 defines a third inner diameterand thus a wall thickness of the tubular portion 308 at the second end334 of the tubular portion 308. The wall thickness of the tubularportion 308 at the second end 334 of the tubular portion 308 ispreferably 0.014 inches and, thus, is larger than the wall thickness ofthe tubular portion 308 between the outer wall 336 and the shoulder 332of the tubular portion 308. The third inner diameter of the aperture 328at the second end 334 of the tubular portion 308 is smaller than thesecond inner diameter of the aperture 328 at the shoulder 332 of thetubular portion 308.

[0073] The outer wall 336 of the tubular portion 308 extends from anundersurface 338 of the bracket portion 310 to the second end 334 of thetubular portion 308. Lobes or ribs 340 extend outwardly from the outerwall 336 of the tubular portion 308. The lobes 340 can be formed in manydifferent configurations on the outer wall 336, but, preferably, thelobes 340 are formed as best illustrated in FIG. 13. As illustrated inFIG. 13, the lobes 340 are axially straight along the outer wall 336such that they extend from the second end 334 of the tubular portion 308to the undersurface 338 of the bracket portion 310. Two different typesof lobes 340 are provided along the outer wall 336, namely high lobes340 a and low lobes 340 b. The high lobes 340 a extend outwardly fromthe outer wall 336 a greater distance than the low lobes 340 b. The highlobes 340 a and the low lobes 340 b are alternated around the outer wall336 such that each high lobe 340 a is positioned between two low lobes340 b and each low lobe 340 b is positioned between two high lobes 340a. Each of the high lobes 340 a also preferably have an angled portion343 a proximate to the undersurface 338 of the bracket portion 310 suchthat the high lobes 340 a extend outwardly further from the outer wall336 proximate to the undersurface 338 of the bracket portion 310 thanproximate to the second end 334 of the tubular portion 308. The purposeof the lobes 340 a, 340 b will be discussed in further detail herein.

[0074] An alternative embodiment of the holding bracket 304 a isillustrated in FIG. 16. The holding bracket 304 a is identical to theholding bracket 304 except with regard to the inner wall 330 a of theaperture 328 a of the tubular portion 308 a. The inner wall 330 a of theholding bracket 304 a has a lip 335 a provided at the second end 334 aof the tubular portion 308 a which defines a fourth inner diameter andthus a wall thickness of the tubular portion 308 a at the second end 334a of the tubular portion 308 a. The wall thickness of the tubularportion 308 a at the second end 334 a is preferably larger than 0.014inches (the wall thickness of the tubular portion 108 at the second end334 of the tubular portion 308 of the holding bracket 304) and, thus, islarger than the wall thickness of the tubular portion 308 a between theouter wall 336 a and the shoulder 332 a of the tubular portion 308 a.The fourth inner diameter of the aperture 328 a at the second end 334 aof the tubular portion 308 a is smaller than the second inner diameterof the aperture 328 a at the shoulder 332 a of the tubular portion 308 a(as well as the third inner diameter of the aperture 328 at the shoulder332 of the tubular portion 308 of the holding bracket 304). The purposefor providing the lip 335 a will be discussed further herein.

[0075] As illustrated in FIGS. 10-12, the nut 302 includes a cylindricalportion 342 and a flat base portion 344 which extends outwardly from thecylindrical portion 342 at one end thereof. The cylindrical portion 342has an aperture 346 therethrough which defines an inner diameter of thecylindrical portion 342. The cylindrical portion 342 at the innerdiameter is generally threaded such that a workpiece, such as a bolt,can be attached thereto. The base portion 344 includes end recesses 347,349 and axially projecting end portions 351, 353 and 355, 357 situatedon opposite sides of the recesses 347, 349, respectively. The recesses347, 349 and sized to accept the protrusions 317, 319 of the holdingbracket 304.

[0076] As illustrated in FIGS. 10-12, the retainer 307 may be a springformed from rectangular wire bent into the form illustrated. Retainer307 is preferably one piece and extends from end portion 361 to sideportion 363, then to middle portion 365, then to side portion 367, andthen to end portion 369. The operation and purpose of the retainer 307will be discussed further herein.

[0077] In operation, the second end 360 of the stem 306 is inserted intothe aperture 328 of the tubular portion 308 of the holding bracket 304at the first end 312 thereof until the enlarged head portion 352 of thestem 306 meets resistance from the shoulder 332 of the inner wall 330 ofthe tubular portion 308, as illustrated in FIG. 12a.

[0078] The nut 302 is then connected to the holding bracket 304 byplacing the base portion 344 of the nut 302 against the base portion 314of the bracket portion 310 such that the protrusions 317, 319 on thebase portion 314 are positioned within the recesses 347, 349 of the nut302. The retainer 307 is then attached to the bracket portion 310 tohold the nut 302 within the confines defined by the bracket portion 310and the retainer 307, but such that the nut 302 is allowed to float bothlaterally and longitudinally to permit alignment of a workpiece, such asa bolt, with the nut 302.

[0079] The retainer 307 is attached to the bracket portion 310 bysqueezing the end portions 361, 369 together until side portions 363,367 are close enough together to fit in the space between the sidewalls316, 318 of the holding bracket 304. The retainer 307 is then placedbetween the sidewalls 316, 318, with the side portions 363, 367 beingaligned with the slots 324, 326. The squeeze force on end portions 361,369 is then released, allowing the side portions 363, 367 to moveoutwardly and into the slots 324, 326, into the position shown in FIGS.11-12.

[0080] The tubular portion 308 of the holding bracket 304 is theninserted into an aperture 364 of a workpiece 366, such that theundersurface 338 of the bracket portion 310 of the holding bracket 304sits on a top surface 368 of the workpiece 366, as illustrated in FIG.12b. The aperture 364 has a diameter which is slightly larger than adiameter of the tubular portion 308 of the holding bracket 304, whichincludes the lobes 340. The aperture 364 has a length which ispreferably larger than or equal to a length of the tubular portion 308of the holding bracket 304 such that the tubular portion 308 does notextend beyond the aperture 364 of the workpiece 366.

[0081] A holding or abutment force F1 is applied to a bottom surface 370of the workpiece 366 and a tool (not shown) engages the tool engagingsection 358 of the stem 306 and applies a force F2 to the stem 306 whichis directed axially and in the opposite direction than the force F1 isapplied to the workpiece 366, as illustrated in FIG. 12b. The force F2on the stem 306 seats the tubular portion 308 and the bracket portion310 of the holding bracket 304 firmly against and within the workpiece366.

[0082] Upon application of force F2 to the stem 306, the enlarged headportion 352 meets resistance from the shoulder 332 of the inner wall 330such that the inner wall 330 is forced to expand radially outwardly asthe enlarged head portion 352 deforms to the size of the expanded innerwall 330, with assistance from the cavity (not shown) in the enlargedhead portion 352, if provided. As the inner wall 330 of the tubularportion 308 is inwardly tapered or stepped from the shoulder 332 to thesecond end 334 of the tubular portion 308, the enlarged head stem 352will consistently have an outer diameter which is larger than thediameter of the inner wall 330 of the tubular portion 308, even thoughthe enlarged stem head 352 deforms to assume the geometry relevant tothe size of the expanded inner wall 330 of the tubular portion 308.Thus, the axial force F2 applied to the enlarged stem head 352 willplace a continuous exertion of radial expansion on the inner wall 330 ofthe tubular portion 308. As the inner wall 330 is continuously expandedby the enlarged head portion 352, the outer wall 336 of the tubularportion 308 continuously expands radially outwardly within the aperture364 against the wall of the workpiece 366, thus embedding the lobes 340a, 340 b in the wall of the workpiece 366 in a fixed and intimateengagement with the wall of the aperture 364.

[0083] The angled portions 343 a of the lobes 340 a embed further intothe wall of the workpiece 366 in comparison to the remainder of thelobes 340 a, to provide improved torque-out of the holding bracket 304.As the high lobes 340 a embed into the wall of the workpiece 366,material of the workpiece 366 is displaced between high lobes 340 a. Thedisplaced material, however, does not always fill the space between thehigh lobes 340 a and, therefore, the low lobes 340 b are provided toboth take up space and act as a seal with the wall of the workpiece 366.

[0084] When the enlarged head portion 352 is pulled completely throughthe aperture 328 of the tubular portion 308, the holding bracket 304 isattached to the workpiece 366, as illustrated in FIG. 12c, and the stem306 can be discarded. A workpiece, such as a bolt, can then be attachedto the nut plate 300.

[0085] The enlarged head portion 352 of the stem 306 will initiallyexpand the tubular portion 308 as well as place a compressive load onthe components to seat them against the upper surface 368 of theworkpiece 366. The tubular portion 308 will expand to engage the wall ofthe aperture 364 in the workpiece 366. As this occurs, radial forces areestablished which are sufficient to deform the head portion 352radially. Thus, the head portion 352 can handle tolerance variations inthe workpiece aperture 364, and will continuously deform the tubularportion 308 radially outward to engage the aperture wall with sufficientforce to cause the lobes 340, or alternate structure, on the outer wall336 of tubular portion 308 to embed in the wall of the aperture 364. Ascan be appreciated, the increasing wall thickness of the tubular portion308 insures that radial deformation continues along the entire length oftubular portion 308 to attain the desired degree of engagement of thelobes 340 in the wall of the aperture 364 such that improved torque-out,push-out and fatigue characteristics are achieved.

[0086] The alternative embodiment of the holding bracket 304 aillustrated in FIG. 16 provides improved push-out characteristics overthe holding bracket 304 as the holding bracket 304 a includes the lip335 a provided at the second end 334 a of the tubular portion 308 a. Asthe lip 335 a is provided, the stem 306 will push and embed even morematerial into the wall of the aperture 364 such that improved push-outcharacteristics are achieved.

[0087] The nut plates 100, 200, 300 of the embodiments of the presentinvention provide for a number of benefits over the nut plates of theprior art. Namely, the nut plates 100, 200, 300 have improvedtorque-out, push-out and fatigue characteristics in comparison to nutplates of the prior art; the nut plates 100, 200, 300 are lighter inweight than nut plates of the prior art, thus reducing operating cost;the nut plates 100, 200, 300 have an increased grip range, thus reducingfastener inventory; the nut plates 100, 200, 300 do not requirecounter-bore/countersink in the workpieces, thus providing for lowerinstallation cost; the nut plates 100, 200, 300 do not require flaring,thus providing for lower installation cost; the nut plates 100, 200, 300do not require any special aperture preparation, thus providing forlower installation cost; the nut plates 100, 200, 300 do not cause a gapto be formed between the tubular portions 108, 208, 308 and the wall ofthe workpiece 166, 266, 366; and the nut plates 100, 200, 300 make useof standard blind rivet installation tooling, thus lowering tool costs.

[0088] It should be noted, however, that flaring of the end of thetubular portions 108, 208, 308 could still be performed by lengtheningthe tubular portions 108, 208, 308 such that it extends beyond thelength of the wall of the workpiece 166, 266, 366. Flaring of the endsof the tubular portions 108, 208, 308 would merely provide a furtherlocking mechanism such that the nut plates 100, 200, 300 would haveincreased torque-out and push-out values.

[0089] It should also be noted that the connection of the nut 102, 202,302 in each of the embodiments of the invention could be performed afterthe attachment of the tubular portion 108, 208, 308 to the wall of theaperture 164, 264, 364 of the workpiece 166, 266, 366 if desired,although this is not preferred.

[0090] The nut 102, 202, 302 can also be removed from the nut plate 100,200, 300 upon wear thereof and replaced with a new nut 102, 202, 302 asdesired.

[0091] While preferred embodiments of the invention are shown anddescribed, it is envisioned that those skilled in the art may devisevarious modifications without departing from the spirit and scope of theforegoing description.

The invention is claimed as follows:
 1. A nut plate adapted to beattached to a wall defined by an aperture through a workpiece, said nutplate comprising: a nut having a base portion and a portion extendingupwardly from said base, said upwardly extending portion having anaperture provided therethrough; a holding bracket including a tubularportion and a bracket portion, said tubular portion having a first endand a second end, said bracket portion extending from said first end ofsaid tubular portion, said tubular portion including an outer wall andan inner wall, said outer wall extending from said first end of saidtubular portion to said second end of said tubular portion, said innerwall extending from said first end of said tubular portion to saidsecond end of said tubular portion, said inner wall being defined by anaperture extending through said tubular portion, said inner wall beingtapered such that a diameter of said aperture at said first end of saidtubular portion is larger than a diameter of said aperture at saidsecond end of said tubular portion, said aperture of said tubular wallbeing in communication with said aperture of said nut; a stem having anenlarged head portion and an elongate portion extending therefrom, saidstem being positioned within said aperture of said tubular portion, saidenlarged head portion capable of expanding said inner wall of saidtubular portion upon axial movement of said stem such that said outerwall of said tubular portion is forced into engagement with the wall ofthe workpiece; and means for securing said nut within said bracketportion, said securing means permitting limited movement of said nutwithin said bracket portion.
 2. A nut plate as defined in claim 1,wherein said upwardly extending portion is cylindrical and wherein aninner wall of said upwardly extending portion defined by said apertureis threaded.
 3. A nut plate as defined in claim 1, wherein said tubularportion of said holding bracket and said bracket portion of said holdingbracket are integrally formed.
 4. A nut plate as defined in claim 1,wherein said inner wall of said tubular portion further defines ashoulder proximate to said first end of said tubular portion, saiddiameter of said aperture at said first end of said tubular portionbeing larger than a diameter of said aperture at said shoulder and saiddiameter of said aperture at said shoulder being larger than saiddiameter of said aperture at said second end of said tubular portion. 5.A nut plate as defined in claim 4, wherein said enlarged head portion ofsaid stem has a diameter which is larger than said diameter of saidaperture at said shoulder but which is smaller than said diameter ofsaid aperture at said first end of said tubular portion such that saidenlarged head portion of said stem is capable of resting upon saidshoulder.
 6. A nut plate as defined in claim 1, wherein said inner wallfurther defines a lip at said second end of said tubular portion suchthat said diameter of said aperture at said second end of said tubularportion is reduced.
 7. A nut plate as defined in claim 1, wherein saidouter wall has a plurality of lobes extending outwardly therefrom, saidlobes capable of being embedded into the wall of the workpiece uponexpansion of said inner wall by the stem.
 8. A nut plate as defined inclaim 7, wherein each said lobe substantially extends from an undersideof said bracket portion to said second end of said tubular portion.
 9. Anut plate as defined in claim 7, wherein adjacent lobes are separated bya gap.
 10. A nut plate as defined in claim 7, wherein each said lobe hasan angled portion proximate to an underside of said bracket portion suchthat each said lobe extends further away from said outer wall proximateto said underside of said bracket portion than from said second end ofsaid tubular portion.
 11. A nut plate as defined in claim 7, whereinsaid plurality of lobes includes high lobes and low lobes, said highlobes extending further outwardly from said outer wall than said lowlobes.
 12. A nut plate as defined in claim 11, wherein each said highlobe has an angled portion proximate to an underside of said bracketportion such that each said high lobe extends further away from saidouter wall proximate to said underside of said bracket portion than fromsaid second end of said tubular portion.
 13. A nut plate as defined inclaim 11, wherein each said high lobe is positioned between two lowlobes, and wherein each said low lobe is positioned between two highlobes.
 14. A nut plate as defined in claim 1, wherein said enlarged headportion of said stem is formed of a material which allows said enlargedhead portion of said stem to deform to a geometrically relevant sizesuch that said enlarged head portion continues to expand said inner wallof said tubular portion until said enlarged head portion exits saidaperture of said tubular portion at said second end thereof.
 15. A nutplate as defined in claim 14, wherein said enlarged head portion of saidstem has a cavity provided therein, said cavity of said enlarged headportion capable of assisting in the deformation of said enlarged headportion.
 16. A nut plate as defined in claim 1, wherein said bracketportion has a base portion which extends outwardly from said first endof said tubular portion and opposing sidewalls which project from saidbase portion in a direction opposite from said tubular portion, saidopposing sidewalls defining a space for receiving said nut.
 17. A nutplate as defined in claim 16, wherein each said sidewall of said bracketportion has a slot therethrough, and wherein said securing meansincludes a flexible retainer that fits over said base portion of saidnut and which includes portions which project into each of said slots ofsaid opposing sidewalls.
 18. A nut plate as defined in claim 17, whereinsaid base portion of said bracket portion has protrusions which projectfrom said base portion of said bracket portion in a direction oppositeof said tubular portion, and wherein said base portion of said nut hasopposite end recesses provided, said opposite end recesses capable ofreceiving said protrusions to limit movement of said nut relative tosaid bracket portion.
 19. A nut plate as defined in claim 16, whereinsaid base portion of said nut has opposite ends having at least one tabmember extending therefrom, and wherein said securing means includes atleast one opening in each said sidewall for receiving a tab member ofsaid nut.
 20. A nut plate as defined in claim 19, wherein at least oneof said sidewalls is formed of a flexible material such that said atleast one sidewall can be flexed away from said other sidewall to allowsaid tab members of said nut to be received in said openings of saidsidewalls.
 21. A nut plate as defined in claim 20, wherein said holdingbracket is separately formed of a bracket and a sleeve, said brackethaving an opening therethrough and said opposing sidewalls with slotstherethrough, and said sleeve having a tubular portion and an enlargedhead at one end thereof, said tubular portion extending through saidopening of said bracket such that said enlarged head of said sleeve ispositioned on said bracket, said enlarged head extending through saidslots of said opposing sidewalls of tubular portion.
 22. A nut plate asdefined in claim 1, wherein said tubular portion has a length which issmaller than a length of the wall of the workpiece such that said secondend of said tubular portion does not extend outside of the aperture ofthe workpiece.
 23. A tubular portion of a nut plate which is adapted tobe attached to a wall defined by an aperture through a workpiece, saidtubular portion being sized to fit within the aperture of the workpiece,said tubular portion comprising: an outer wall extending generally froma first end of said tubular portion to a second end of said tubularportion; and an inner wall extending from said first end of said tubularportion to said second end of said tubular portion, said inner wallbeing defined by an aperture extending through said tubular portion,said inner wall being tapered such that a diameter of said aperture atsaid first end of said tubular portion is larger than a diameter of saidaperture at said second end of said tubular portion; said aperture ofsaid tubular portion capable of receiving a stem therethrough forexpanding said inner wall of said tubular portion such that said outerwall of said tubular portion is forced into engagement with the wall ofthe workpiece.
 24. A tubular portion as defined in claim 23, whereinsaid inner wall further defines a shoulder proximate to said first endof said tubular portion, said diameter of said aperture at said firstend of said tubular portion being larger than a diameter of saidaperture at said shoulder and said diameter of said aperture at saidshoulder being larger than said diameter of said aperture at said secondend of said tubular portion.
 25. A tubular portion as defined in claim23, wherein said inner wall further defines a lip at said second end ofsaid tubular portion such that said diameter of said aperture at saidsecond end of said tubular portion is reduced.
 26. A tubular portion asdefined in claim 23, wherein said outer wall has a plurality of lobesextending outwardly therefrom, said lobes capable of being embedded intothe wall of the workpiece upon expansion of said inner wall by the stem.27. A tubular portion as defined in claim 26, wherein each said lobesubstantially extends from proximate to said first end of said tubularportion to said second end of said tubular portion.
 28. A tubularportion as defined in claim 26, wherein adjacent lobes are separated bya gap.
 29. A tubular portion as defined in claim 26, wherein each saidlobe has an angled portion proximate to said first end of said tubularportion such that each said lobe extends further away from said outerwall proximate to said first end of said tubular portion than from saidsecond end of said tubular portion.
 30. A tubular portion as defined inclaim 26, wherein said plurality of lobes includes high lobes and lowlobes, said high lobes extending further outwardly from said outer wallthan said low lobes.
 31. A tubular portion as defined in claim 30,wherein each said high lobe has an angled portion proximate to saidfirst end of said tubular portion such that each said high lobe extendsfurther away from said outer wall proximate to said first end of saidtubular portion than from said second end of said tubular portion.
 32. Atubular portion as defined in claim 30, wherein each said high lobe ispositioned between two low lobes, and wherein each said low lobe ispositioned between two high lobes.
 33. A tubular portion as defined inclaim 23, wherein said tubular portion has a length which is smallerthan a length of the wall of the workpiece such that said second end ofsaid tubular portion does not extend outside of the aperture of theworkpiece.
 34. A tubular portion of a nut plate which is adapted to beattached to a wall defined by an aperture through a workpiece, saidtubular portion being sized to fit within the aperture of the workpiece,said tubular portion comprising: an outer wall extending from a firstend of said tubular portion to a second end of said tubular portion,said outer wall having a plurality of lobes extending outwardlytherefrom, at least a portion of said lobes having an angled portionproximate to said first end of said tubular portion such that each saidlobe having an angled portion extends further away from said outer wallproximate to said first end of said tubular portion than from saidsecond end of said tubular portion; and an inner wall extending fromsaid first end of said tubular portion to said second end of saidtubular portion, said inner wall being defined by an aperture extendingthrough said tubular portion; said aperture of said tubular portioncapable of receiving a stem therethrough for expanding said inner wallof said tubular portion such that said outer wall of said tubularportion is forced into engagement with the wall of the workpiece, saidlobes capable of being embedded into the wall of the workpiece uponexpansion of said inner wall by the stem.
 35. A tubular portion asdefined in claim 34, wherein each said lobe substantially extends fromproximate to said first end of said tubular portion to said second endof said tubular portion.
 36. A tubular portion as defined in claim 34,wherein adjacent lobes are separated by a gap.
 37. A tubular portion asdefined in claim 34, wherein said plurality of lobes includes high lobesand low lobes, said high lobes extending further outwardly from saidouter wall than said low lobes.
 38. A tubular portion as defined inclaim 37, wherein each said high lobe has said angled portion proximateto said first end of said tubular portion such that each said high lobeextends further away from said outer wall proximate to said first end ofsaid tubular portion than from said second end of said tubular portion.39. A tubular portion as defined in claim 37, wherein each said highlobe is positioned between two low lobes, and wherein each said low lobeis positioned between two high lobes.
 40. A tubular portion as definedin claim 34, wherein said tubular portion has a length which is smallerthan a length of the wall of the workpiece such that said second end ofsaid tubular portion does not extend outside of the aperture of theworkpiece.
 41. A stem of a nut plate which is adapted to be attached toa wall defined by an aperture through a workpiece, said stem capable ofexpanding a tapered inner wall of a tubular portion of the nut plateupon axial movement thereof such that an outer wall of the tubularportion is engaged with the wall of the workpiece, said stem comprising:an elongated portion; and a deformable head portion provided at an endof said elongated portion, said deformable head portion allowing formeasured expansion of the tapered inner wall of the tubular portion tocompensate for variations in the size of the aperture of the workpiecesuch that the outer wall provides adequate engagement with the wall ofthe workpiece, said deformable head portion deforming when adequateresistance is exerted thereon by the workpiece during axial movement ofthe stem.
 42. A stem as defined in claim 41, wherein said deformablehead portion has a cavity provided therein.
 43. A method of securing anut plate to a wall defined by an aperture through a workpiece, saidmethod comprising the steps of: a) providing said nut plate whichincludes a nut, a holding bracket having a tubular portion and a bracketportion extending from a first end thereof, said tubular portion havingan outer wall with lobes protruding outwardly therefrom, said tubularportion having an aperture provided therethrough which defines an innerwall of said tubular portion, said inner wall defining a shoulderproximate to said first end of said tubular portion, said inner wallbeing tapered from said shoulder to a second end of said tubularportion, and a stem having an enlarged head portion; b) inserting saidstem into said aperture of said tubular portion such that said enlargedhead portion of said stem is positioned on said shoulder of said innerwall of said tubular portion; c) placing said nut into said bracketportion; d) securing said nut within said bracket portion such that saidnut is prevented from moving out of said bracket portion but such thatsaid nut is free to move within said bracket portion; e) inserting saidtubular portion into the aperture of the workpiece such that anundersurface of said bracket portion is positioned on a top surface ofthe workpiece; f) applying a first force to a bottom surface of theworkpiece; g) applying a second force to said stem to move said enlargedhead portion of said stem through said aperture of said tubular portionsuch that said tapered inner wall of said aperture is expanded to forcesaid lobes on said outer wall to embed into the wall of the workpiece tosecure said tubular portion to the workpiece.
 44. A method as defined inclaim 43, further including the step of: a) deforming said enlarged headportion of said stem to a geometrically relevant size relative to saidtapered inner wall upon expansion thereof such that said enlarged headportion continues to expand said tapered inner wall.